Hot melt adhesives are often formed and packaged into solid blocks, e.g., pellets, chubs, pillows, and blocks. Solid blocks are preferred over powder for there is less risk associated with inhalation during loading and unloading, and convenience associated with storing and shipping them. It is also desirable for the adhesives to be provided in a form that can be stored and thereafter automatically transported and fed into the application devices in an application site. Free-flowing, agglomeration resistant free-flowing pellets are desirable to decrease disruption for end-use operators.
Conventional techniques to pelletize soft and tacky plastic materials, as described in U.S. Pat. No. 5,041,251, include extruding and cutting the materials in a cooling fluid, and the pellets remain in the cooling fluid for at least several hours to days. The pellets are separated from the cooling fluid and dusted with wax powder to impart nontackiness. Waxes typically have high crystallinity, and thus aid in free flowing.
Amorphous poly-alpha-olefin (APAO) based adhesives have low crystallinity, are inherently soft and tacky, and tend to agglomerate (block) into a huge mass at elevated temperatures. Agglomerated adhesives disrupt end-use operations because agglomerated mass must be forcibly re-dispersed. To prevent such agglomeration, APAO based adhesives are typically packaged in drums or as individual chubs, blocks and pillows with a protective packaging; or transported in cooled, insulated rail cars. Due to the above limitations, pellet adhesives are typically formed from high crystalline adhesives, such as ethylene vinyl acetates and high crystalline olefin based adhesives, and not from APAO based adhesives.
There is a need in the art for producing pellets of amorphous poly-alpha-olefin based adhesives in a faster throughput that resists agglomeration. The current invention fulfills this need.